is there a shorthand to access an optional throwing an exception if it's not set?

# announcements

[iex]

is there a shorthand to access an optional throwing an exception if it's not set?

[thana]

orElseThrow?

[rax]

You mean something like this but shorter?

myOptional ?: throw Error("myOptional")

[iex]

don't see it in autocompletions 🤔

[iex]

yeah but I'd like to chain it. I tried writing this:

fun <T> T?.unwrap(errorMsg: String): T =
    this ?: error(errorMsg)

[iex]

But it doesn't get rid of the optional when chaining:

[iex]

inputs.cough?.unwrap("Cough not set").type = type // error after ), because it's missing ?

[iex]

so all I can do now is

(inputs.cough ?: error("Cough not set")).type = type

[iex]

which is probably not so bad

[thana]

Ah its a nullable not the type Optional 🤓

[thana]

requireNotNull already exists in kotlin

[rax]

@iex I see. You can sort of do this using experimental feature: contracts.

Given:

@ExperimentalContracts
fun <T> T.unwrap(errorMessage: String): T {
    contract {
        returns()
    }
    return this ?: throw Error(errorMessage)
}

Usage:

val a: String?
a = null
a?.unwrap("a is Null!!")
a // a would smart cast to not-null here.

[rax]

It's used by requireNotNull, checkNotNull @thana recommended.

[thana]

btw the way the shortest shortcut is !! if you don't care for the concrete error 🙈

[rax]

The ultimate shortcut

[iex]

oh that with contracts is interesting

[iex]

aware of !! 😉 I wanted an error message

[iex]

thanks!